Photolithography and laser writing are processes that are typically utilized when defining regions or portions of surfaces in the manufacture of semiconductor devices. The resolving power inherent in these processes is adequate when working with feature sizes larger than about three microns. When it is desired to form a contact opening, for example through a layer of silicon oxide, to expose only the top surface of a very narrow feature, such as a one micron gate, it is quite difficult to adequately align the opening. Often, such openings extend beyond the lateral limits of the gate resulting in the metal contact shortng out the transistor. Similarly, when it is desired to dope regions of a semiconducting body formed on both sides of a very narrow mesa without doping the mesa itself, these processes are not helpful.
The present invention is a process of the self-aligning type which permits defining a portion of only the top surface of a very narrow mesa. The portion of the top surface may then receive a protective layer to prevent doping of the mesa while forming doped regions in the semiconductor body adjacent the mesa. Optionally, the portion of the top surface may be exposed for subsequent doping of that surface or formation of an ohmic contact thereon without shorting to adjacent regions.